CTHRC1 Induces Pancreatic Stellate Cells (PSCs) into Myofibroblast-like Cancer-Associated Fibroblasts (myCAFs)

[BACKGROUND] Collagen triple helix repeat containing-1 (CTHRC1) is a secreted protein that contributes to the progression of various cancers, including pancreatic cancer. The higher expression of CTHRC1 in tumor tissues is associated with poorer survival outcomes. However, its specific roles in tumor extracellular matrix (ECM) remodeling remain unclear. Our study aims to investigate the influences of CTHRC1 on pancreatic stellate cells (PSCs), a main source of ECM production in pancreatic cancer. [METHODS AND RESULTS] The analyses of the publicly available pancreatic cancer patient data revealed that CTHRC1 is mainly expressed in cancer stroma and highly correlated with ECM-related genes. An in vitro study showed that more than 40% of these genes can be upregulated by CTHRC1. CTHRC1 specifically activated PSC into myofibroblast-like cancer-associated fibroblasts (myCAFs), which are characterized by a significantly upregulated POSTN gene expression. Periostin (coded by the POSTN gene) has a central role in the CTHRC1-PSCs-cancer metastasis axis. Furthermore, CTHRC1 promoted pancreatic cancer cell proliferation through PSC activation to a greater extent than via direct stimulation. Proof-of-concept experiments showed that the long-term (4-week) inhibition of CTHRC1 led to significant tumor suppression and ECM reduction, and also resulted in an unexpected shift in the CAF subtype from myCAFs to inflammatory CAFs (iCAFs). [CONCLUSION] PSC activation was demonstrated to be the key molecular mechanism responsible for the tumor-promoting effects of CTHRC1, and CTHRC1 has a critical role in CAF subtype differentiation and tumor microenvironment (TME) remodeling. The inhibition of CTHRC1 as a therapeutic strategy for the treatment of pancreatic cancer warrants further investigation.

Abstract 1347: PAUF stimulates monocytes and induces their differentiation into tumor-associated macrophages

Background: One of the main reasons for the failure of cancer treatments is that the biological function of therapeutic target molecules is only studied in cancer cells. Therefore, the dynamic and complex interactions between cancer and stromal cells in the tumor microenvironment (TME) should be investigated. TME-specific stromal cells include various cells, with tumor-associated macrophages (TAMs) being one of the major players. TAM are differentiated from monocytes, as immature monocytes recognize molecules derived from infected cells or foreign substances, become activated, and may differentiate into anti-tumoral M1 macrophages or pro-tumoral M2 macrophages (called TAMs). TAMs induce immune evasion of cancer cells in the TME, leading to active proliferation and metastasis of cancer cells. The presence of TAMs in the TME is associated with poor prognosis in various cancers.

PAUF is a protein that is secreted by cancer cells, and it exerts tumor-promoting effects through autocrine and paracrine mechanisms. Compared to the autocrine actions, the paracrine effects of PAUF on immune cells in the TME are less understood.

Objective: This study aimed to evaluate 1) the role of PAUF as a TME modulator, and specifically, a TAM inducer and 2) the potentiality of PAUF antibody as a blocker of TAM transformation.

Methods and Results: In a monocyte-PAUF co-culture system, PAUF (tested at two concentrations, 0.1 and 0.5 μg/mL) demonstrated strong chemoattractant effects on monocytes (~400% of that caused by PBS), which were blocked by TLR2/4 inhibitors. PAUF also induced differentiation of monocytes into macrophages, which were identified to be TAM, using flow cytometric analysis and ELISA method. Moreover, these PAUF-induced TAM demonstrated T cell suppressing capacities. Finally, in a CFPAC-1 human cancer orthotopic mouse model, a humanized monoclonal PAUF-antibody diminished 60-70% of infiltrated TAM (p<0.01), quantified using an immunofluorescence assay (IFA).

Conclusion: In conclusion, this study provides direct evidence that PAUF can differentiate monocytes into TAM of immune-suppressing functions, and the PAUF neutralization-induced TAM infiltration blocking suggests potential combination use of PAUF antibody with immunotherapeutics for cancer treatments.

Citation Format: Fen Jiang, Yeon Jeong Kim, Yun Yong Park, Tae Heung Kang, Sang Seok Koh. PAUF stimulates monocytes and induces their differentiation into tumor-associated macrophages [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 1347.

PAUF Induces Migration of Human Pancreatic Cancer Cells Exclusively via the TLR4/MyD88/NF-κB Signaling Pathway

PAUF, a tumor-promoting protein secreted by cancer cells, exerts paracrine effects on immune cells through TLR4 receptors expressed on immune cell surfaces. This study aimed to investigate if PAUF elicits autocrine effects on pancreatic cancer (PC) cells through TLR4, a receptor that is overexpressed on PC cells. In this study, TLR4 expression was detected in PC cells only, but not normal pancreatic cells. The migration of TLR4 high-expressing PC cells (i.e., BxPC-3) was reduced by a selective TLR4 inhibitor, in a dose-dependent manner. Using TLR4 overexpressed and knockout PC cell lines, we observed direct PAUF-TLR4 binding on the PC cell surfaces, and that PAUF-induced cancer migration may be mediated exclusively through the TLR4 receptor. Further experiments showed that PAUF signaling was passed down through the TLR4/MyD88 pathway without the involvement of the TLR4/TRIF pathway. TLR4 knockout also downregulated PC membrane PD-L1 expression, which was not influenced by PAUF. To the best of our knowledge, TLR4 is the first receptor identified on cancer cells that mediates PAUF’s migration-promoting effect. The results of this study enhanced our understanding of the mechanism of PAUF-induced tumor-promoting effects and suggests that TLR4 expression on cancer cells may be an important biomarker for anti-PAUF treatment.

First-in-class monoclonal antibody (mAb) PBP1510 targeting pancreatic adenocarcinoma upregulated factor (PAUF) for pancreatic cancer (PC) treatment: Preclinical perspectives

e16274

Background: PAUF has been shown to induce PC cell proliferation, angiogenesis and evasion of immune surveillance, thereby promoting tumour progression and metastasis. PBP1510, a novel humanized IgG1 mAb developed by Prestige Biopharma Limited, Singapore, binds to and neutralizes PAUF with high specificity and affinity. With no available targeted therapies against PAUF, the first in its class, PBP1510, has been granted Orphan Drug Designation by EMA, US FDA and Korea MFDS. Methods: To assess inhibition of migration and invasion of PC in vitro, PC cell lines (CFPAC-1 and BxPC-3) with high expression levels of PAUF, and primary PC cells extracted from patients were treated with PBP1510 or human IgG (negative control). Suitability of cynomolgus monkey as animal model for pharmacokinetic (PK) and toxicity studies was verified by comparing binding affinities of PBP1510 to human and monkey PAUF. PK characteristics and immunogenicity of PBP1510 (up to 20 mg/kg), were examined in single dose studies in 6 monkeys. A 4-week repeated dose toxicity study was also conducted in 32 monkeys with PBP1510 (up to 40 mg/kg). An in vitro tissue cross-reactivity study was also conducted in a full panel of normal human tissues, to assess potential toxicity in humans. Results: PBP1510 suppressed the proliferation of the PC cell lines compared to negative control. The migration and invasion of PBP1510 treated PC cell lines as well as the primary tumour cells from patients was significantly reduced compared to the respective control groups in vitro. Similarity in binding affinity of PBP1510 to human PAUF and monkey PAUF, and amino acid sequence homology between human and monkey PAUF, suggest that monkey is an appropriate animal species for toxicity and PK studies of PBP1510. In monkey studies, a dose-proportional increase in systemic exposure was observed at low and high doses. PBP1510 at doses up to 40 mg/kg was well tolerated by study animals and no notable local or systemic toxicity was observed. Low immunogenic profile of PBP1510 was indicated by an absence of anti-PBP1510 antibodies till up to 57 days (8 doses and 28-day recovery period). These data are used to simulate human PK profile and to derive the starting dose and maximum escalated dose for the upcoming Phase 1 clinical studies. Cross-reactivity results did not reveal non-specific binding of PBP1510 in the human tissues except in the cytoplasm of acinar and duct epithelium in the salivary gland which is not expected to be of major toxicologic significance. Conclusions: The efficacy and safety data presented here, along with the data from in vivo mouse studies demonstrating superior anti-tumour activity of PBP1510 treatment, support further clinical development of PBP1510 as a novel anti-cancer agent to treat PAUF-positive PC. The pivotal step of advancing PBP1510 into initial human studies is now in progress.

PAUF as a Target for Treatment of High PAUF-Expressing Ovarian Cancer

Pancreatic adenocarcinoma up-regulated factor (PAUF) plays an important role in tumor growth, metastasis, and immune evasion in the pancreatic tumor microenvironment, and recent studies suggest an association between PAUF expression and poor prognosis in ovarian cancer patients. The current study aimed 1) to characterize the potential tumor-promoting role of PAUF in ovarian cancer, using in vitro and in vivo models, including a PAUF-knockout OVCAR-5 cell line, and 2) to explore the potential therapeutic effects of an anti-PAUF antibody for ovarian cancer. Recombinant PAUF significantly increased tumor metastatic capacity (migration, invasion, and adhesion) in all the ovarian cancer cell lines tested, except for the OVCAR-5 cell line which expresses PAUF at a much higher level than the other cells. PAUF-knockout in the OVCAR-5 cell line led to apparently delayed tumor growth in vitro and in vivo. Furthermore, the administration of an anti-PAUF antibody exhibited notable sensitizing and synchronizing effects on docetaxel in mice bearing the OVCAR-5 xenograft tumors. Taken together, this study shows that the expression level of PAUF is an independent factor determining malignant behaviors of ovarian cancer and, for the first time, it suggests that PAUF may be a promising therapeutic target for high PAUF-expressing ovarian cancer.

Translocalization of enhanced PKM2 protein into the nucleus induced by cancer upregulated gene 2 confers cancer stem cell-like phenotypes

Increased mRNA levels of cancer upregulated gene (CUG)2 have been detected in many different tumor tissues using Affymetrix microarray. Oncogenic capability of the CUG2 gene has been further reported. However, the mechanism by which CUG2 overexpression promotes cancer stem cell (CSC)-like phenotypes remains unknown. With recent studies showing that pyruvate kinase muscle 2 (PKM2) is overexpressed in clinical tissues from gastric, lung, and cervical cancer patients, we hypothesized that PKM2 might play an important role in CSC-like phenotypes caused by CUG2 overexpression. The present study revealed that PKM2 protein levels and translocation of PKM2 into the nucleus were enhanced in CUG2-overexpressing lung carcinoma A549 and immortalized bronchial BEAS-2B cells than in control cells. Ex-pression levels of c-Myc, CyclinD1, and PKM2 were increased in CUG2-overexpressing cells than in control cells. Furthermore, EGFR and ERK inhibitors as well as suppression of Yap1 and NEK2 expression reduced PKM2 protein levels. Interestingly, knockdown of β-catenin expression failed to reduce PKM2 protein levels. Furthermore, reduction of PKM2 expression with its siRNA hindered CSC-like phenotypes such as faster wound heal-ing, aggressive transwell migration, and increased size/number of sphere formation. The introduction of mutant S37A PKM2-green fluorescence protein (GFP) into cells without ability to move to the nucleus did not confer CSC-like phenotypes, whereas forced expression of wild-type PKM2 promoted such phenotypes. Overall, CUG2-induced increase in the expression of nuclear PKM2 contributes to CSC-like phenotypes by upregulating c-Myc and CyclinD1 as a co-activator.

Translocalization of enhanced PKM2 protein into the nucleus induced by cancer upregulated gene 2 confers cancer stem cell-like phenotypes

Increased mRNA levels of cancer upregulated gene (CUG)2 have been detected in many different tumor tissues using Affymetrix microarray. Oncogenic capability of the CUG2 gene has been further reported. However, the mechanism by which CUG2 overexpression promotes cancer stem cell (CSC)-like phenotypes remains unknown. With recent studies showing that pyruvate kinase muscle 2 (PKM2) is overexpressed in clinical tissues from gastric, lung, and cervical cancer patients, we hypothesized that PKM2 might play an important role in CSC-like phenotypes caused by CUG2 overexpression. The present study revealed that PKM2 protein levels and translocation of PKM2 into the nucleus were enhanced in CUG2-overexpressing lung carcinoma A549 and immortalized bronchial BEAS-2B cells than in control cells. Expression levels of c-Myc, CyclinD1, and PKM2 were increased in CUG2-overexpressing cells than in control cells. Furthermore, EGFR and ERK inhibitors as well as suppression of Yap1 and NEK2 expression reduced PKM2 protein levels. Interestingly, knockdown of β-catenin expression failed to reduce PKM2 protein levels. Furthermore, reduction of PKM2 expression with its siRNA hindered CSC-like phenotypes such as faster wound healing, aggressive transwell migration, and increased size/number of sphere formation. The introduction of mutant S37A PKM2-green fluorescence protein (GFP) into cells without ability to move to the nucleus did not confer CSC-like phenotypes, whereas forced expression of wild-type PKM2 promoted such phenotypes. Overall, CUG2-induced increase in the expression of nuclear PKM2 contributes to CSC-like phenotypes by upregulating c-Myc and CyclinD1 as a co-activator. [BMB Reports 2022;55(2): 98-103].

Monocarboxylate transporter 9 (MCT9) is down-regulated in renal cell carcinoma

BACKGROUND

The renal cell carcinoma (RCC) incidences are continuously increasing, however, their proper characterization remains difficult. Mammalian kidneys require large amounts of energy, and monocarboxylate transporter (MCT) gene family is responsible for the transport of monocarboxylic compounds across plasma membranes.

OBJECTIVE

A total of 14 MCT members have been identified in humans, which show highly distinct substrate affinities and tissue distributions. To understand the yet-uncharacterized renal cancer-specific role of MCTs, we identified MCT members that are differentially regulated during the renal tumor progression.

METHODS

We examined the expression level of MCT members in renal cell tumors and their relationship with survival rate of patients using a public database. Quantitative RT-PCR and northern blotting were performed to validate the expression of MCTs. Anti-MCT9 antiserum was raised in rabbit and used to examine MCT9 expression in normal and tumor tissue arrays. Effect of MCT9 overexpression on cell proliferation was measured using renal cancer cell lines.

RESULTS

MCT9 was found to be abundantly and exclusively expressed in human kidney cells, and was highly downregulated in renal cancers. Kaplan-Meier plotter analysis revealed an increased survival rate of MCT9 high-expressing RCC patients. MCT9 proteins were detected in normal kidney tissue sections and their overexpression clearly attenuated renal cell proliferation.

CONCLUSIONS

MCT9 was identified as a novel highly downregulated gene in renal cell cancer, and its overexpression clearly attenuated RCC cell proliferation. Thus, functional analysis of MCT9 may help in deciphering a yet-undiscovered kidney-specific energy metabolism during renal tumor progression.

Overexpression of Cancer Upregulated Gene 2 (CUG2) Decreases Spry2 Through c-Cbl, Leading to Activation of EGFR and β-Catenin Signaling

Purpose

The mechanism by which cancer upregulated gene 2 (CUG2) overexpression induces cancer stem cell-like phenotypes is not fully understood. Because the increased activity and expression of epidermal growth factor receptor (EGFR) kinase have been reported in A549 cancer cells overexpressing CUG2 (A549-CUG2) compared with control cells (A549-Vec), the Sprouty2 (Spry2) protein has gained attention as the downstream molecule of EGFR signaling. Therefore, we aim to identify the role of Spry2 in CUG2-overexpressing lung cancer cells.

Materials and Methods

Spry2 expression levels were examined in A549-CUG2 and A549-Vec cells by Western blotting and qRT-PCR. Cell migration, invasion, and sphere formation were examined after Spry2 suppression and overexpression. EGFR-Stat1 and Akt-ERK protein phosphorylation levels were detected via immunoblotting. NEK2 kinase and β-catenin reporter assay were performed for downstream of Spry2 signaling.

Results

Although A549-CUG2 cells showed lower levels of the Spry2 protein than A549-Vec cells, no difference in levels of Spry2 transcript was observed between both cells via qRT-PCR. Furthermore, MG132 treatment enhanced the protein levels and ubiquitination of Spry2, suggesting that Spry2 protein expression can be regulated via the ubiquitin-proteasome pathway. The enforced expression of c-Cbl, known as the binding partner of Spry2, decreased the Spry2 protein levels, whereas its knockdown oppositely increased them. Epithelial-mesenchymal transition (EMT) and sphere formation were increased in A549-Vec cells during Spry2 siRNA treatment, confirming the role of Spry2 in CUG2-induced oncogenesis. Furthermore, EMT and sphere formation were determined by the Spry2 protein levels through the regulation of EGFR-Stat1 and β-catenin-NEK2-Yap1 signaling pathways.

Conclusion

CUG2 reduces Spry2 protein levels, the negative signaling molecule of cell proliferation, via c-Cbl, possibly activating the EGFR and β-catenin signaling pathways and, in turn, contributing to the induction of cancer stem cell-like phenotypes.

Phosphofructokinase 1 Platelet Isoform Promotes β-Catenin Transactivation for Tumor Development

Metabolism plays a critical role in direct regulation of a variety of cellular activities via metabolic enzymes and metabolites. Here, we demonstrate that phosphofructokinase 1 platelet isoform (PFKP), which catalyzes a rate-limiting reaction in glycolysis, promotes EGFR activation-induced nuclear translocation and activation of β-catenin, thereby enhancing the expression of its downstream genes CCND1 and MYC in human glioblastoma cells. Importantly, we showed that EGFR-phosphorylated PFKP Y64 has a critical role in AKT activation and AKT-mediated β-catenin S552 phosphorylation and subsequent β-catenin transactivation and promotion of tumor cell glycolysis, migration, invasion, proliferation, and brain tumor growth. These findings highlight a novel mechanism underlying a glycolytic enzyme-mediated β-catenin transactivation and underscore the integrated and reciprocal regulation of metabolism and gene expression, which are two fundamental biological processes in tumor development.

CGK062, a small chemical molecule, inhibits cancer upregulated gene 2‑induced oncogenesis through NEK2 and β‑catenin

The mechanisms through which cancer‑upregulated gene 2 (CUG2), a novel oncogene, affects Wnt/β‑catenin signaling, essential for tumorigenesis, are unclear. In this study, we aimed to elucidate some of these mechanisms in A549 lung cancer cells. Under the overexpression of CUG2, the protein levels and activity of β‑catenin were evaluated by western blot analysis and luciferase assay. To examine a biological consequence of β‑catenin under CUG2 overexpression, cell migration, invasion and sphere formation assay were performed. The upregulation of β‑catenin induced by CUG2 overexpression was also accessed by xenotransplantation in mice. We first found that CUG2 overexpression increased β‑catenin expression and activity. The suppression of β‑catenin decreased cancer stem cell (CSC)‑like phenotypes, indicating that β‑catenin is involved in CUG2‑mediated CSC‑like phenotypes. Notably, CUG2 overexpression increased the phosphorylation of β‑catenin at Ser33/Ser37, which is known to recruit E3 ligase for β‑catenin degradation. Moreover, CUG2 interacted with and enhanced the expression and kinase activity of never in mitosis gene A‑related kinase 2 (NEK2). Recombinant NEK2 phosphorylated β‑catenin at Ser33/Ser37, while NEK2 knockdown decreased the phosphorylation of β‑catenin, suggesting that NEK2 is involved in the phosphorylation of β‑catenin at Ser33/Ser37. Treatment with CGK062, a small chemical molecule, which promotes the phosphorylation of β‑catenin at Ser33/Ser37 through protein kinase C (PKC)α to induce its degradation, reduced β‑catenin levels and inhibited the CUG2‑induced features of malignant tumors, including increased cell migration, invasion and sphere formation. Furthermore, CGK062 treatment suppressed CUG2‑mediated tumor formation in nude mice. Taken together, the findings of this study suggest that CUG2 enhances the phosphorylation of β‑catenin at Ser33/Ser37 by activating NEK2, thus stabilizing β‑catenin. CGK062 may thus have potential for use as a therapeutic drug against CUG2‑overexpressing lung cancer cells.

Cancer upregulated gene (CUG)2 elevates YAP1 expression, leading to enhancement of epithelial-mesenchymal transition in human lung cancer cells

Although our previous studies have showed that a novel oncogene, cancer upregulated gene (CUG)2 induced epithelial-mesenchymal transition (EMT), the detailed molecular mechanism remains unknown. Because several lines of evidence documented that Yes-Associated Protein (YAP)1 is closely associated with cancer stem cell (CSC)-like phenotypes including EMT, stemness, and drug resistance, we wondered if YAP1 is involved in CUG2-induced EMT. We herein found that the overexpression of CUG2 increased YAP1 expression at the transcriptional as well as protein levels. Chromatin immunoprecipitation assay revealed that the elevated YAP1 transcripts are attributed to c-Jun and AP2 bindings to the YAP1 promoter. Akt and MAPK kinases including ERK, JNK, and p38 MAPK enhanced the level of YAP1 protein. In spite of a close relationship between β-catenin and YAP1, not β-catenin but NEK2 played the role in increasing YAP1 expression. Silencing YAP1 inhibited CUG2-induced cell migration and invasion. N-cadherin and vimentin expressions were decreased during YAP1 knockdown. The suppression of YAP1 diminished TGF-β transcriptional activity and expression as well as phosphorylation level of Smad2 and Twist protein. Conversely, LY2109761 or Smad2 siRNA treatment reduced YAP1 protein levels, indicating a close interplay between YAP1 and TGF-β signaling. Taken together, we suggest that CUG2 induces up-regulation of YAP1 expression, leading to enhancing CUG2-induced EMT via a close crosstalk between YAP1 and TGF-β signaling.

STAT1‑HDAC4 signaling induces epithelial‑mesenchymal transition and sphere formation of cancer cells overexpressing the oncogene, CUG2

Our previous studies have shown that the novel oncogene, cancer upregulated gene 2 (CUG2), activates STAT1, which is linked to anticancer drug resistance, induces epithelial-mesenchymal transition (EMT) and cancer stem cell-like phenotypes as determined by MTT, migration and sphere formation assays. We thus aimed to ascertain whether the activation of STAT1 by CUG2 is involved in these malignant phenotypes besides drug resistance. Here, we showed that STAT1 suppression decreased the expression of N-cadherin and vimentin, biomarkers of EMT, which led to inhibition of the migration and invasion of human lung A549 cancer cells stably expressing CUG2, but did not recover E-cadherin expression. STAT1 siRNA also diminished CUG2-induced TGF-β signaling, which is critical in EMT, and TGF-β transcriptional activity. Conversely, inhibition of TGF-β signaling reduced phosphorylation of STAT1, indicating a crosstalk between STAT1 and TGF-β signaling. Furthermore, STAT1 silencing diminished sphere formation, which was supported by downregulation of stemness-related factors such as Sox2, Oct4, and Nanog. Constitutive suppression of STAT1 also inhibited cell migration, invasion and sphere formation. As STAT1 acetylation counteracts STAT1 phosphorylation, acetylation of STAT1 by treatment with trichostatin A, an inhibitor of histone deacetylases (HDACs), reduced cell migration, invasion, and sphere formation. As HDAC4 is known to target STAT1, its role was investigated under CUG2 overexpression. HDAC4 suppression resulted in inhibition of cell migration, invasion, and sphere formation as HDAC4 silencing hindered TGF-β signaling and decreased expression of Sox2 and Nanog. Taken together, we suggest that STAT1-HDAC4 signaling induces malignant tumor features such as EMT and sphere formation in CUG2-overexpressing cancer cells.

Elevated expression of pancreatic adenocarcinoma upregulated factor (PAUF) is associated with poor prognosis and chemoresistance in epithelial ovarian cancer

Pancreatic adenocarcinoma upregulated factor (PAUF) is a ligand of toll-like receptors (TLRs) and has been reported to be involved in pancreatic tumor development. However, the significance of PAUF expression in epithelial ovarian cancer remains unclear. We aimed to investigate the possible clinical significance of PAUF in epithelial ovarian cancer. We examined the link between PAUF and TLR4 in ovarian cancer cell lines. Recombinant PAUF induced cell activation and proliferation in ovarian cancer cell lines, whereas PAUF knockdown inhibited these properties. Subsequently, we assessed PAUF and TLR4 expression by immunohistochemistry on tissue microarray of 408 ovarian samples ranging from normal to metastatic. PAUF expression positively correlated with TLR4 expression. Overexpression of PAUF was associated with high-grade tumor (p = 0.014) and chemoresistant tumor (p = 0.017). Similarly, high expression of TLR4 correlated with advanced tumor stage (p = 0.002) and chemoresistant tumor (p = 0.001). Multivariate analysis indicated that PAUF^high, TLR4^high, and PAUF^high/TLR4^high expression are independent prognostic factor for progression-free survival, while TLR4^high and PAUF^high/TLR4^high expression were independent prognostic factors for overall survival. Our results suggest that PAUF has a role in ovarian cancer progression and is a potential prognostic marker and novel chemotherapeutic target for ovarian cancer.

Cancer upregulated gene 2 induces epithelial-mesenchymal transition of human lung cancer cells via TGF-β signaling

Cancer upregulated gene 2 (CUG2) enhances cell migration and invasion, but the underlying mechanism has not been revealed. Herein, CUG2 decreased the expression of E-cadherin and increased the expression of N-cadherin and vimentin, characteristics of the epithelial-mesenchymal transition (EMT). A CUG2 deletion mutant, lacking interaction with nucleophosmin 1 (NPM1), or suppression of NPM1 reduced wound healing and cell invasion, indicating that CUG2-mediated EMT requires NPM1. CUG2 enhanced activation of Smad2/3 and expression of Snail and Twist, while the CUG2 silence decreased these TGF-β signaling pathways, leading to suppression of EMT. NPM silence also inhibited the CUG2-induced TGF-β signaling. These results suggest that TGF-β signaling is involved in CUG2-induced EMT. Treatment with EW-7197, a novel inhibitor of TGF-β signaling, diminished CUG2-mediated EMT and inhibition of Akt, ERK, JNK, and p38 MAPK, non-canonical TGF-β signaling molecules, also decreased expression of Smad2/3, Snail and Twist, leading to inhibition of EMT. The results confirm that TGF-β signaling is essential for CUG2-mediated EMT. Interestingly, TGF-β enhanced CUG2 expression. We further found that both CUG2-induced TGF-β production and TGF-β-induced CUG2 up-regulation required a physical interaction between Sp1 and Smad2/3 in the CUG2 and TGF-β promoter, as demonstrated by a promoter reporter assay, immunoprecipitation, and ChIP assay. These results indicated close crosstalk between CUG2 and TGF-β. Conversely, suppression of CUG2 or NPM1 did not completely inhibit TGF-β-induced EMT, indicating that the effect of TGF-β on EMT is dominant over the effect of CUG2 on EMT. Collectively, our findings suggest that CUG2 induces the EMT via TGF-β signaling.

DCPP1 is the mouse ortholog of human PAUF that possesses functional analogy in pancreatic cancer

Pancreatic adenocarcinoma upregulated factor (PAUF) overexpressed in pancreatic ductal adenocarcinoma (PDAC) plays a major role in tumor progression and metastasis by autocrine and paracrine manners. However, underlying molecular mechanism of PAUF functioning in pancreatic cancer are not fully understood yet. The objective of this study was to evaluate the potential of demilune cell and parotid protein 1 (DCPP1) as a putative mouse ortholog of human PAUF by sequence alignment and functional studies. Overexpression of mouse DCPP1 in Chinese hamster ovary (CHO) cells or pancreatic cancer cells increased cell proliferation, migration, invasion, and adhesion ability in vitro. Treatment of human pancreatic cancer cells with recombinant mouse DCPP1 elevated cell growth, motility, invasiveness, and adhesiveness. Mouse DCPP1 exerted its function on pancreatic cancer cells by activating intracellular signaling pathways involved in aggressive cancer phenotype of human pancreatic cancer cells. Moreover, subcutaneous injection of mice with DCPP1-overexpressing CHO cells increased tumor sizes. Taken together, we conclude that mouse DCPP1 is a multifunctional promoter of tumor growth through functional activation of pancreatic cancer cells, suggesting it to be an ortholog of human PAUF.

Characterization of VNTRs Within the Entire Region of SLC6A3 and Its Association with Hypertension

The dopamine transporter SLC6A3 (DAT1) mediates uptake of dopamine into presynaptic terminals. In addition, in previous reports, hypertensive rats were associated with DAT gene, but the genetic association with SLC6A3 and hypertension is still unknown. We examined the distribution of variable number of tandem repeats (VNTRs) and conducted polymorphic analysis of the entire region of SLC6A3. Ten VNTR regions (MS1-10) were revealed throughout the intronic and UTRs; seven VNTR regions were newly isolated and three VNTRs were previously reported. Four VNTR regions (SLC6A3-MS1, -MS4, -MS8 [rs3836790], and -MS9 [rs28363170]) showed polymorphism and these loci were found to be transmitted through meiosis following Mendelian inheritance. These VNTR polymorphisms may be useful markers for paternity mapping and DNA fingerprinting. Furthermore, we also conducted a case-control study between the controls and essential hypertensive cases. Analysis of the genotypes of SLC6A3-MS8 (rs3836790) revealed that having an 8/6-repeat allele, which was only detected in hypertensive cases, was associated with hypertension (p < 0.05). Additional significant association was identified between the short 7-repeat allele of SLC6A3-MS9 (rs28363170) and the occurrence of hypertension (odds ratio 2.02; p < 0.05). These results revealed the genetic association between SLC6A3 and hypertension, and the specific VNTR alleles of SLC6A3 may be a risk factor for hypertension.

Pancreatic adenocarcinoma upregulated factor serves as adjuvant by activating dendritic cells through stimulation of TLR4

Dendritic cell (DC) based cancer vaccines represent a promising immunotherapeutic strategy against cancer. To enhance the modest immunogenicity of DC vaccines, various adjuvants are often incorporated. Particularly, most of the common adjuvants are derived from bacteria. In the current study, we evaluate the use of a human pancreatic cancer derived protein, pancreatic adenocarcinoma upregulated factor (PAUF), as a novel DC vaccine adjuvant. We show that PAUF can induce activation and maturation of DCs and activate NFkB by stimulating the Toll-like receptor signaling pathway. Furthermore, vaccination with PAUF treated DCs pulsed with E7 or OVA peptides leads to generation of E7 or OVA-specific CD8+ T cells and memory T cells, which correlate with long term tumor protection and antitumor effects against TC-1 and EG.7 tumors in mice. Finally, we demonstrated that PAUF mediated DC activation and immune stimulation are dependent on TLR4. Our data provides evidence supporting PAUF as a promising adjuvant for DC based therapies, which can be applied in conjunction with other cancer therapies. Most importantly, our results serve as a reference for future investigation of human based adjuvants.

A polymorphic minisatellite region of BORIS regulates gene expression and its rare variants correlate with lung cancer susceptibility

Aberrant expression of BORIS/CTCFL (Brother of the Regulator of Imprinted Sites/CTCF-like protein) is reported in different malignancies. In this study, we characterized the entire promoter region of BORIS/CTCFL, including the CpG islands, to assess the relationship between BORIS expression and lung cancer. To simplify the construction of luciferase reporter cassettes with various-sized portions of the upstream region, genomic copies of BORIS were isolated using TAR cloning technology. We analyzed three promoter blocks: the GATA/CCAAT box, the CpG islands and the minisatellite region BORIS-MS2. Polymorphic minisatellite sequences were isolated from genomic DNA prepared from the blood of controls and cases. Of the three promoter blocks, the GATA/CCAAT box was determined to be a critical element of the core promoter, while the CpG islands and the BORIS-MS2 minisatellite region were found to act as regulators. Interestingly, the polymorphic minisatellite region BORIS-MS2 was identified as a negative regulator that repressed the expression levels of luciferase reporter cassettes less effectively in cancer cells compared with normal cells. We also examined the association between the size of BORIS-MS2 and lung cancer in a case–control study with 590 controls and 206 lung cancer cases. Rare alleles of BORIS-MS2 were associated with a statistically significantly increased risk of lung cancer (odds ratio, 2.04; 95% confidence interval, 1.02–4.08; and P=0.039). To conclude, our data provide information on the organization of the BORIS promoter region and gene regulation in normal and cancer cells. In addition, we propose that specific alleles of the BORIS-MS2 region could be used to identify the risk for lung cancer.

A basal-like breast cancer-specific role for SRF-IL6 in YAP-induced cancer stemness

The switch between stem/progenitor cell expansion and differentiation is critical for organ homeostasis. The mammalian Hippo pathway effector and oncoprotein YAP expands undifferentiated stem/progenitor cells in various tissues. However, the YAP-associated transcription factors and downstream targets underlying this stemness-promoting activity are poorly understood. Here we show that the SRF–IL6 axis is the critical mediator of YAP-induced stemness in mammary epithelial cells and breast cancer. Specifically, serum response factor (SRF)-mediated binding and recruitment of YAP to mammary stem cell (MaSC) signature-gene promoters induce numerous MaSC signature genes, among which the target interleukin (IL)-6 is critical for YAP-induced stemness. High SRF–YAP/TAZ expression is correlated with IL6-enriched MaSC/basal-like breast cancer (BLBC). Finally, we show that this high SRF expression enables YAP to more efficiently induce IL6 and stemness in BLBC compared with luminal-type breast cancer. Collectively, our results establish the importance of SRF–YAP–IL6 signalling in promoting MaSC-like properties in a BLBC-specific manner.

The downstream effector of the Hippo pathway, YAP, is a critical regulator of both normal and cancer stem cell properties. In this study, the authors show that in basal-like breast tumors YAP forms a complex with SRF and together they induce a mammary stem cell gene signature through the transcriptional activation of IL-6.

NDR1 modulates the UV-induced DNA-damage checkpoint and nucleotide excision repair

Nucleotide excision repair (NER) is the sole mechanism of UV-induced DNA lesion repair in mammals. A single round of NER requires multiple components including seven core NER factors, xeroderma pigmentosum A-G (XPA-XPG), and many auxiliary effector proteins including ATR serine/threonine kinase. The XPA protein helps to verify DNA damage and thus plays a rate-limiting role in NER. Hence, the regulation of XPA is important for the entire NER kinetic. We found that NDR1, a novel XPA-interacting protein, modulates NER by modulating the UV-induced DNA-damage checkpoint. In quiescent cells, NDR1 localized mainly in the cytoplasm. After UV irradiation, NDR1 accumulated in the nucleus. The siRNA knockdown of NDR1 delayed the repair of UV-induced cyclobutane pyrimidine dimers in both normal cells and cancer cells. It did not, however, alter the expression levels or the chromatin association levels of the core NER factors following UV irradiation. Instead, the NDR1-depleted cells displayed reduced activity of ATR for some set of its substrates including CHK1 and p53, suggesting that NDR1 modulates NER indirectly via the ATR pathway.

A PAUF-neutralizing antibody targets both carcinoma and endothelial cells to impede pancreatic tumor progression and metastasis

Pancreatic adenocarcinoma up-regulated factor (PAUF) is expressed in pancreatic ductal adenocarcinoma (PDAC) and plays an important role in tumor progression and metastasis. Here we evaluate the anti-tumor efficacy of a human monoclonal antibody against PAUF, PMAb83, to provide a therapeutic intervention to treat the disease. PMAb83 reduced tumor growth and distant metastasis in orthotopically xenografted mice of human PDAC cells. PMAb83 treatment retarded proliferation along with weakened aggressiveness traits of the carcinoma cells. AKT/β-catenin signaling played a role in the carcinoma cell proliferation and the treated xenograft tumors exhibited reduced levels of β-catenin and cyclin D1. Moreover PMAb83 abrogated the PAUF-induced angiogenic responses of endothelial cells, reducing the density of CD31(+) vessels in the treated tumors. In combination with gemcitabine, PMAb83 conferred enhanced survival of xenografted mice by about twofold compared to gemcitabine alone. Taken together, our findings show that PMAb83 treatment decreases the aggressiveness of carcinoma cells and suppresses tumor vascularization, which culminates in mitigated tumor growth and metastasis with improved survival in PDAC mouse models.

Effect of exposure to interleukin-21 at various time points on human natural killer cell culture

BACKGROUND AIMS

Interleukin-21 (IL-21) can enhance the effector function of natural killer (NK) cells but also limits their proliferation when continuously combined with IL-2/IL-15. Paradoxically, membrane-bound (mb)-IL-21 has been shown to improve human NK cell proliferation when cultured with IL-2/mb-IL-15. To clarify the role of IL-21, we investigated the effect of the timing of IL-21 addition to NK cell culture.

METHODS

IL-2/IL-15-activated NK cells were additionally treated with IL-21 according to the following schedules; (i) control (without IL-21); (ii) first week (day 0 to day 7); (iii) intermittent (the first 3 days of each week for 7 weeks); (iv) after 1 week (day 8 to day 14); and (v) continuous (day 0 to day 49). The expression of NK receptors, granzyme B, perforin, CD107a, interferon-γ, telomere length and NK cell death were measured by flow cytometry.

RESULTS

Compared with the control (2004.2-fold; n = 10 healthy donors) and intermittent groups (2063.9-fold), a strong proliferative response of the NK cells on day 42 was identified in the "first week" group (3743.8-fold) (P < 0.05). NK cells treated with IL-21 in the "first week" group showed cytotoxicity similar to that in control cells. On day 28, there was a significant increase in cytotoxicity of "first week" NK cells that received IL-21 treatment for an additional 2 days compared with the "first week" NK cells (P < 0.05).

CONCLUSIONS

These data suggest that controlling temporal exposure of IL-21 during NK cell proliferation can be a critical consideration to improve the yields and cytotoxicity of NK cells.

Acetylshikonin induces apoptosis of hepatitis B virus X protein-expressing human hepatocellular carcinoma cells via endoplasmic reticulum stress

Since it has been known that shikonin derived from a medicinal plant possesses anti-cancer activity, we wonder whether acetylshikonin (ASK), a derivate of shikonin, can be used to treat hepatocellular carcinoma cells expressing hepatitis B virus X protein (HBX), an oncoprotein from hepatitis B virus. When ASK was added to Hep3B cells stably expressing HBX, it induced apoptosis in a dose-dependent manner. ASK induced upregulation and export of Nur77 to the cytoplasm and activation of JNK. Likewise, suppression of Nur77 and JNK inactivation protected the cells from ASK-induced apoptosis, indicating that Nur77 upregulation and JNK activation were required for ASK-mediated apoptosis. Furthermore, ASK increased the expression of Bip and ubiquitination levels of cellular proteins, features of endoplasmic reticulum (ER) stress, via the production of reactive oxygen species in a dose-dependent manner. Suppression of reactive oxygen species with N-acetylcysteine reduced levels of Bip protein and ubiquitination levels of cellular proteins during ASK treatment, leading to protection of cells from apoptosis. Cycloheximide treatment reduced ASK-induced ER stress, suggesting that protein synthesis is involved in ASK-induced ER stress. Moreover, we showed using salubrinal, an ER stress inhibitor that reactive oxygen species production, JNK activation, and Nur77 upregulation and its translocation to cytoplasm are necessary for ER-induced stress. Interestingly, we found that JNK inactivation suppresses ASK-induced ER stress, whereas Nur77 siRNA treatment does not, indicating that JNK is required for ASK-induced ER stress. Accordingly, we report that ASK induces ER stress, which is prerequisite for apoptosis of HBX-expressing hepatocellular carcinoma cells.

Feroniellin A-induced autophagy causes apoptosis in multidrug-resistant human A549 lung cancer cells

During the screening of natural chemicals that can reverse multidrug resistance in human A549 lung cancer cells resistant to etoposide (A549RT-eto), we discovered that Feroniellin A (FERO), a novel furanocoumarin, shows toxicity toward A549RT-eto cells in a dose- and time-dependent manner. FERO reduced the expression of NF-κB, leading to downregulation of P-glycoprotein (P-gp), encoded by MDR1, which eventually sensitized A549RT-eto cells to apoptosis. FERO specifically diminished transcription and promoter activity of MDR1 but did not inhibit the expression of other multidrug resistance genes MRP2 and BCRP. Moreover, co-administration of FERO with Bay11-7802, an inhibitor of NF-κB, accelerated apoptosis of A549RT-eto cells through decreased expression of P-gp, indicating that NF-κB is involved in multidrug resistance. Conversely, addition of Z-VAD, a pan-caspase inhibitor, blocked FERO-induced apoptosis in A549RT-eto cells but did not block downregulation of P-gp, indicating that a decrease in P-gp expression is necessary but not sufficient for FERO-induced apoptosis. Interestingly, we found that FERO also induces autophagy, which is characterized by the conversion of LC3 I to LC3 II, induction of GFP-LC3 puncta, enhanced expression of Beclin-1 and ATG5, and inactivation of mTOR. Furthermore, suppression of Beclin-1 by siRNA reduced FERO-induced apoptosis in A549RT-eto cells and activation of autophagy by rapamycin accelerated FERO-induced apoptosis, suggesting that autophagy plays an active role in FERO-induced apoptosis. Herein, we report that FERO reverses multidrug resistance in A549RT-eto cells and exerts its cytotoxic effect by induction of both autophagy and apoptosis, which suggests that FERO can be a useful anticancer drug for multidrug-resistant lung cancer.

Suppression of autophagic genes sensitizes CUG2-overexpressing A549 human lung cancer cells to oncolytic vesicular stomatitis virus-induced apoptosis

We showed in our previous study that cancer upregulated gene (CUG) 2, a novel oncogene, confers resistance to infection of oncolytic vesicular stomatitis virus (VSV) by activating Stat1-mediated signal transduction. Since many studies have reported that autophagy is involved in virus replication, we investigated whether autophagy also plays a role in the antiviral activity in A549 cells overexpressing CUG2 (A549-CUG2). We suppressed Atg5 or Beclin 1 expression using siRNA and examined its effect on the susceptibility of cells to infection by oncolytic VSV. We found that A549-CUG2 cells treated with Atg5 or Beclin 1 siRNA became susceptible to VSV infection, whereas A549-CUG2 cells treated with control siRNA were resistant. This result suggests that autophagy is involved in the antiviral response of A549-CUG2 cells. Further investigation revealed that autophagy impairment enhanced the generation of reactive oxygen species (ROS), which resulted in inactivation of S6 kinase. Under these conditions, the levels of ISG15 transcript and protein decreased, which conferred on A549-CUG2 cell susceptibility to VSV infection. Finally, we found that overloading of H₂O₂ sensitized control A549-CUG2 cells to VSV-induced apoptosis. Taken together, these results indicate that autophagy impairment induces excessive ROS formation, which decreases S6 kinase activity and ISG15 expression, ultimately rendering the A549-CUG2 cells susceptible to VSV infection. We propose that autophagy impairment is a potential strategy for successful VSV virotherapy of CUG2-overexpressing tumors.

Efficient targeting and tumor retardation effect of pancreatic adenocarcinoma up-regulated factor (PAUF)-specific RNA replacement in pancreatic cancer mouse model

The soluble protein pancreatic adenocarcinoma up-regulated factor (PAUF) plays an important role in pancreatic tumor progression and has begun to attract attention as a therapeutic target for pancreatic cancer. We herein present PAUF RNA-targeting gene therapy strategies with both targeting and therapeutic function using trans-splicing ribozyme (TSR) in pancreatic cancer. We developed adenoviral PAUF-targeting TSR (Rz) containing a PAUF-specific internal guide sequence (IGS) determined by library screening. This Rz harbors suicide gene, herpes simplex virus thymidine kinase (HSV-tk) or firefly luciferase (Luc) as a transgene for 3' exon replacement of PAUF RNAs. Ad-Rz-TK, Rz harboring the HSV-tk, showed significant inhibition of tumor growth in vivo as well as PAUF-dependent cell death in vitro via a successful trans-splicing reaction. Selective induction of Rz-controlled transgene in PAUF-expressing pancreatic cancer was confirmed through noninvasive in vivo imaging; a luminescence signal from Rz harboring Luc (Ad-Rz-Luc) was detectable only in pancreatic tumor sites, not in normal mice. In addition, a [(125)I] FIAU signal reflecting thymidine kinase expression through SPECT and ex vivo biodistribution was co-localized with the tumor sites when we treated with Ad-Rz-TK in orthotopic xenograft model. Taken together, these results imply that PAUF-targeting TSR can contribute to successful targeted gene therapy for pancreatic cancer.

Cancer upregulated gene 2, a novel oncogene, confers resistance to oncolytic vesicular stomatitis virus through STAT1-OASL2 signaling

We have recently found a novel oncogene, named cancer upregulated gene 2 (CUG2), which activates Ras and mitogen-activated protein kinases (MAPKs), including ERK, JNK and p38 MAPK. Because activation of these signaling pathways has previously been shown to enhance cancer cell susceptibility to oncolysis by certain viruses, we examined whether vesicular stomatitis virus (VSV) could function as a potential therapeutic agent by efficiently inducing cytolysis in cells transformed by CUG2. Unexpectedly, NIH3T3 cells stably expressing CUG2 (NIH-CUG2) were resistant to VSV because of the activation of signal transducers and activators of transcription 1 (STAT1). The result was supported by evidence showing that suppression of STAT1 with short interference RNA (siRNA) renders cells susceptible to VSV. Furthermore, 2'-5' oligoadenylate synthetase-like (OASL) 2 was the most affected by STAT1 expression level among anti-viral proteins and furthermore suppression of OASL2 mRNA level caused NIH-CUG2 cells to succumb to VSV as seen in NIH-CUG2 cells treated with STAT1 siRNA. In addition, Colon26L5 carcinoma cells stably expressing CUG2 (Colon26L5-CUG2) exhibited resistance to VSV, whereas Colon26L5 stably expressing a control vector yielded to VSV infection. Moreover, Colon26L5-CUG2 cells stably suppressing STAT1 succumbed to VSV infection, resulting in apoptosis. Taken together, we propose that VSV treatment combined with the selective regulation of genes such as STAT1 and OASL2 will improve therapeutic outcomes for CUG2-overexpressing tumors.

Collagen triple helix repeat containing-1 promotes pancreatic cancer progression by regulating migration and adhesion of tumor cells

Collagen triple helix repeat containing-1 (CTHRC1) is a secreted protein involved in vascular remodeling, bone formation and developmental morphogenesis. CTHRC1 has recently been shown to be expressed in human cancers such as breast cancer and melanoma. In this study, we show that CTHRC1 is highly expressed in human pancreatic cancer tissues and plays a role in the progression and metastasis of the disease. CTHRC1 promoted primary tumor growth and metastatic spread of cancer cells to distant organs in orthotopic xenograft tumor mouse models. Overexpression of CTHRC1 in cancer cells resulted in increased motility and adhesiveness, whereas these cellular activities were diminished by down-regulation of the protein. CTHRC1 activated several key signaling molecules, including Src, focal adhesion kinase, paxillin, mitogen-activated protein kinase kinase (MEK), extracellular signal-regulated kinase and Rac1. Treatment with chemical inhibitors of Src, MEK or Rac1 and expression of dominant-negative Rac1 attenuated CTHRC1-induced cell migration and adhesion. Collectively, our results suggest that CTHRC1 has a role in pancreatic cancer progression and metastasis by regulating migration and adhesion activities of cancer cells.

SIRT1 inhibits proliferation of pancreatic cancer cells expressing pancreatic adenocarcinoma up-regulated factor (PAUF), a novel oncogene, by suppression of β-catenin

Because we found in a recent study that pancreatic adenocarcinoma up-regulated factor (PAUF), a novel oncogene, induces a rapid proliferation of pancreatic cells by up-regulation of β-catenin, we postulated that β-catenin might be a target molecule for pancreatic cancer treatment. We thus speculated whether SIRT1, known to target β-catenin in a colon cancer model, suppresses β-catenin in those pancreatic cancer cells that express PAUF (Panc-PAUF). We further evaluated whether such suppression would lead to inhibition of the proliferation of these cells. The ectopic expression of either SIRT1 or resveratrol (an activator of SIRT1) suppressed levels of β-catenin protein and its transcriptional activity in Panc-PAUF cells. Conversely, suppression of SIRT1 expression by siRNA enhanced β-catenin expression and transcriptional activity. SIRT1 mutant analysis showed that nuclear localization of SIRT1 is not required for reduction of β-catenin. Treatment with MG132, a proteasomal inhibitor, restored β-catenin protein levels, suggesting that SIRT1-mediated degradation of β-catenin requires proteasomal activity. It was reported that inhibition of GSK-3β or Siah-1 stabilizes β-catenin in colon cancer cells, but suppression of GSK-3β or Siah-1 using siRNA in the presence of resveratrol instead diminished β-catenin protein levels in Panc-PAUF cells. This suggests that GSK-3β and Siah-1 are not involved in SIRT1-mediated degradation of β-catenin in the cells. Finally, activation of SIRT1 inhibited the proliferation of Panc-PAUF cells by down-regulation of cyclin-D1, a target molecule of β-catenin. These results suggest that SIRT1 activation may be a therapeutic strategy for treatment of pancreatic cancer cells that express PAUF via the down-regulation of β-catenin.

Hepatitis B virus X protein inhibits extracellular IFN-α-mediated signal transduction by downregulation of type I IFN receptor

We have previously shown that hepatitis B virus (HBV) protein X (HBX), a regulatory protein of HBV, activates Stat1, leading to type I interferon (IFN) production. Type I IFN secreted from HBX-expressing hepatic cells enforces antiviral signals through its binding to the cognate type I IFN receptor. We therefore investigated how cells handle this detrimental situation. Interestingly, compared to Chang cells stably expressing an empty vector (Chang-Vec), Chang cells stably expressing HBX (Chang-HBX) showed lower levels of IFN-α receptor 1 (IFNAR1) protein, a subunit of type I IFN receptor. The levels of IFNAR1 transcripts detected in Chang-HBX cells were lower than the levels in Chang-Vec cells, indicating that HBX regulates IFNAR1 at the transcriptional level. Moreover, we observed that HBX induced the translocation of IFNAR1 to the cytoplasm. Consistent with these observations, HBX also downregulated Tyk2, which is required for the stable expression of IFNAR1 on the cell surface. Eventually, Chang-HBX cells consistently maintained a lower level of IFNAR1 expression and displayed no proper response to IFN-α, while Chang-Vec cells exhibited a proper response to IFN-α treatment. Taken together, we propose that HBX downregulates IFNAR1, leading to the avoidance of extracellular IFN-α signal transduction.

L1 cell adhesion molecule and epidermal growth factor receptor activation confer cisplatin resistance in intrahepatic cholangiocarcinoma cells

Intrahepatic cholangiocarcinoma (ICC) is refractory to conventional chemotherapy. We previously generated chemoresistant ICC (SCK(R)) cells and showed that AKT and ERK signaling conferred cisplatin resistance. Here, we report that epidermal growth factor receptor (EGFR) signaling and L1 cell adhesion molecule (L1CAM) conferred cisplatin resistance in SCK(R) cells in an additive fashion. Activation of EGFR connected to AKT and ERK signaling pathways may induce anti-apoptosis and promote cell proliferation, while L1CAM promoted cell proliferation by mainly activating ERK signaling. Inhibition of EGFR activation or L1ACM greatly sensitized the cells to cisplatin. EGFR and L1CAM may be important targets for ICC therapy.

Pancreatic adenocarcinoma up-regulated factor (PAUF) enhances the expression of β-catenin, leading to a rapid proliferation of pancreatic cells

It is not yet understood how the enhanced expression of pancreatic adenocarcinoma up-regulated factor (PAUF; a novel oncogene identified in our recent studies), contributes to the oncogenesis of pancreatic cells. We herein report that PAUF up-regulates the expression and transcriptional activity of β-catenin while the suppression of PAUF by shRNA down-regulates β-catenin. The induction of b-catenin by PAUF is mediated by the activities of Akt and GSK-3β, but inhibition of downstream ERK does not reduce β-catenin expression. To test whether PAUF emulates either the Wnt3a-mediated or the protein kinase A-mediated signaling pathway for the stabilization of β-catenin, we examined the phosphorylation status of β-catenin in the presence of PAUF compared with that of β-catenin during treatment with Wnt3a or dibutyryl cAMP, a cell permeable cyclic AMP analogue. PAUF expression induces phosphorylation at Ser-33/37/Thr-41 and Ser-675 of β-catenin but no phosphorylation at Ser-45, indicating that a unique phosphorylation pattern of b-catenin is caused by PAUF. Finally, the expression of PAUF up-regulates both cyclin-D1 and c-Jun, target genes of β-catenin, leading to a rapid proliferation of pancreatic cells; conversely decreased PAUF expression (by shRNA) results in the reduced proliferation of pancreatic cells. Treatment with hexachlorophene (an inhibitor of β-catenin) reduces the proliferation of pancreatic cells despite the presence of PAUF. Taken together, we propose that PAUF can up-regulate and stabilize β-catenin via a novel pattern of phosphorylation, thereby contributing to the rapid proliferation of pancreatic cancer cells.

PAUF promotes adhesiveness of pancreatic cancer cells by modulating focal adhesion kinase

Pancreatic cancer is a notorious disease with a poor prognosis and low survival rates, which is due to limited advances in understanding of the molecular mechanism and inadequate development of effective treatment options over the decades. In previous studies, we demonstrated that a novel soluble protein named pancreatic adenocarcinoma up-regulated factor (PAUF) acts on tumor and immune cells and plays an important role in metastasis and progression of pancreatic cancer. Here we show that PAUF promotes adhesiveness of pancreatic cancer cells to various extracellular matrix (ECM). Our results further support a positive correlation of activation and expression of focal adhesion kinase (FAK), a key player in tumor cell metastasis and survival, with PAUF expression. PAUF-mediated adhesiveness was significantly attenuated upon blockade of the FAK pathway. Moreover, PAUF appeared to enhance resistance of pancreatic cancer cells to anoikis via modulation of FAK. Our results suggest that PAUF-mediated FAK activation plays an important role in pancreatic cancer progression.

Up-regulation of Foxo4 mediated by hepatitis B virus X protein confers resistance to oxidative stress-induced cell death

The hepatitis B virus X (HBX) protein, a regulatory protein of the hepatitis B virus (HBV), has been shown to generate reactive oxygen species (ROS) in human liver cell lines; however, the mechanism by which cells protect themselves under this oxidative stress is poorly understood. Here, we show that HBX induces the up-regulation of Forkhead box class O 4 (Foxo4) not only in Chang cells stably expressing HBX (Chang-HBX) but also in primary hepatic tissues from HBX-transgenic mice. HBX also increased ROS, but reduction of the abundance of ROS using N-acetylcystein (NAC) diminished the levels of Foxo4. Elevated Foxo4 was also detected in nuclei of Chang-HBX cells but not in Chang cells stably expressing the vector (Chang-Vec), suggesting that HBX activates the transcriptional activity of Foxo4. When we examined whether HBX bypasses JNK signaling that targets Foxo4, we found that the activity of JNK but not of ERK is required for the up-regulation of Foxo4 even in the presence of HBX. Furthermore, the reduction of Foxo4 levels using siRNA or a JNK inhibitor rendered Chang-HBX cells sensitive to apoptosis under oxidative stress, suggesting that up-regulation of Foxo4 mediated by HBX enhances resistances to oxidative stress-induced cell death. Accordingly, we propose that Foxo4 may be a useful target for suppression in the treatment of HBV-associated hepatocellular carcinoma cells.

Abstract 101: Claudin-4 overexpression is associated with epigenetic derepression in gastric carcinoma

The tight junction protein claudin-4 is aberrantly up-regulated in gastric cancer, but its clinical significance and the molecular mechanism underlying claudin-4 overexpression in gastric cancer remain unclear. Here, we investigated its roles and epigenetic mechanism regulating CLDN4 expression in gastric cancer. We show that increased membranous expression of claudin-4 in gastric carcinoma is associated with better patient prognosis, whereas cytoplasmic claudin-4 expression didn't show a significant association with prognosis. Consistent with the correlation of increased membranous claudin-4 with favorable clinicopathological factors, claudin-4 overexpression inhibited the migration and invasion of gastric cancer cells; in contrast, it didn't affect cell growth. Claudin-4 expression also increased the barrier function of tight junctions. Claudin-4 up-regulation was strongly correlated with DNA hypomethylation in both gastric tissues and gastric cancer cells. Moreover, loss of repressive histone methylations and gain of active histone modifications were associated with CLDN4 overexpression in gastric cancer cells. Interestingly, CLDN4 repression could be markedly derepressed by combined treatments that simultaneously target both histone modifications and DNA demethylation in CLDN4-hypermethylated cells, whereas concomitant changes in histone methylations and acetylations are required for CLDN4 induction in CLDN4-repressed cells with low DNA methylation. Taken together, this study reveals that membranous claudin-4 expression is associated with gastric cancer progression as well as it is an independent positive prognosis marker in gastric carcinoma. Furthermore, our findings suggest that epigenetic derepression may be a possible mechanism underlying CLDN4 overexpression in gastric cancer and that claudin-4 may have potential as a promising target for the treatment of gastric cancer.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 101. doi:10.1158/1538-7445.AM2011-101

The protease inhibitor, elafin, induces p53-dependent apoptosis in human melanoma cells

Expression of the protease inhibitor elafin is deregulated in several human cancers. However, functions of the protein in cancer are yet to be established. Here, we show that elafin elicits pro-apoptotic effects in melanoma cells but not in normal melanocytes. Elafin triggered the intrinsic apoptotic pathway as evidenced by the increased caspase 9 activity and unaltered caspase 8 activity. Caspase 9-specific siRNA, but not caspase 8-specific siRNA, dramatically abrogated elafin-induced apoptosis. Elevated level of p53 was observed, resulting in increased transcriptional activation and consequent expression of downstream effector molecules (Bax, Puma, Noxa, p21). Moreover, the apoptotic effect of elafin was inhibited by p53-specific siRNA and the p53 inhibitor pifithrin-alpha. Elafin treatment of xenograft mice of melanoma cells led to significantly smaller tumor sizes compared with those of untreated control mice. Immunohistochemical analysis revealed decreased elafin expression in melanoma tissue specimens. Western blot and reverse transcription analyses indicated transcriptional repression of the elafin gene in melanoma cells. Our results collectively indicate that elafin induces apoptosis in melanoma cells through a p53-dependent intrinsic apoptotic pathway, and that repression of elafin expression in melanoma may contribute to disease progression.

Abstract 4406: A monoclonal antibody targeting PAUF inhibits metastasis of pancreatic cancer

Pancreatic cancer is one of the deadliest human tumors and, due to lack of effective therapeutic agents and diagnostic tools, has a poor prognosis with approximately a five-year survival rate of less than 5%. This disease is characterized by early metastatic spread but the process of tumor cell dissemination is largely unknown. Recently, we have shown that a novel soluble protein named PAUF (Pancreatic Adenocarcinoma Up-regulated Factor) plays an important role in the metastasis and progression of the disease. The expression of CXCR4 is induced by PAUF, implicating a role of PAUF in the organ specific metastasis of pancreatic cancer. The tumorigenic and metastatic activity of PAUF suggests that PAUF could be a target for pancreatic cancer immunotherapy. To examine the therapeutic potential of PAUF, a human monoclonal antibody against PAUF (8F3) has been generated. The 8F3 antibody exerted inhibition of migration, invasion, adhesion and proliferation of pancreatic cancer cells in vitro. In combination with gemcitabine, 8F3 showed additive effect on reduction of cell growth. In orthotopically xenografted mouse model, these anti-tumor activities of 8F3 converted to growth retardation and repression of metastasis. The level of PAUF in tumor and serum from 8F3 treated mouse was lower than that of control mouse. The immunohistochemical analysis revealed that the treatment of 8F3 inhibited the proliferation and CXCR4 expression in both primary and metastasized tumors. The 8F3 antibody also alters intracellular signaling which was induced by PAUF. We will also discuss about the effect of 8F3 in tumor microenvironment, especially recruitment of immune cells. Collectively, these findings indicate that PAUF has a therapeutic potential for treatment of human pancreatic cancer and the 8F3 antibody can be developed for therapeutic agent for this disease.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 4406.

Reovirus infection induces apoptosis of TRAIL-resistant gastric cancer cells by down-regulation of Akt activation

The tumor necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL) has been used to treat a variety of cancer cells. However, since some gastric cancer cells are resistant to TRAIL, we explored whether reovirus induces cytolysis in TRAIL-resistant gastric cancer cells. We found that TRAIL-resistant SNU-216 gastric cancer cells were susceptible to apoptosis by reovirus infection. Furthermore, co-treatment with reovirus and TRAIL accelerated apoptosis of SNU-216 cells by down-regulation of Akt activation as assessed by a very low activation of Akt in TRAIL-sensitive SNU-668 gastric cancer cells. Inhibition of Akt signaling with wortmannin or suppression of Akt expression with sh-Akt lentivirus promoted reovirus-mediated apoptosis of SNU-216 gastric cancer cells. Reovirus infection also down-regulates the activation of signaling molecules such as Ras and ERK involved in cell proliferation and survival but not the activation of p38 MAPK involved in cellular stress. In addition, the co-treatment with reovirus and TRAIL resulted in cleavage of caspase-8, caspase-9 and Bid, leading to a decrease in the mitochondrial membrane potential, indicating that reovirus may utilize the mitochondrial intrinsic apoptotic pathway in TRAIL-resistant SNU-216 gastric cancer cells. Accordingly, we first demonstrate that reovirus infection down-regulates Akt activation, leading to apoptosis of TRAIL-resistant gastric cancer cells.

CUG2, a novel oncogene confers reoviral replication through Ras and p38 signaling pathway

As we have recently found a novel oncogene, the cancer-upregulated gene 2 (CUG2), which was elevated in a variety of tumor tissues such as the ovary, liver, lung and pancreas, we examined whether reovirus could efficiently induce cytolysis in cancer cells expressing CUG2 and thus be used as a potential cancer therapeutic agent. In this study, we describe experiments in which we use reovirus to treat NIH3T3 cells stably expressing either CUG2 (NIH-CUG2) or vector only (NIH-Vec). NIH-CUG2 cells readily support reoviral proliferation and undergo apoptosis, whereas NIH-Vec cells are highly resistant to reoviral infection and virus-induced apoptosis. This notable result may be explained by the observation that CUG2 expression inhibits PKR activation, leading to reoviral proliferation in nonpermissive NIH3T3 cells. Furthermore, reovirus infection results in almost complete regression of tumorgenic NIH-CUG2 cells in transplanted nude mice. As we found that CUG2 enhances activation of MAPK (ERK, JNK and p38), Src kinase and Ras, we examined whether CUG2 confers reoviral replication independent of the Ras or p38 MAPK signaling pathway. From these experiments we found that either inhibition of p38 MAPK or Ras blocks reoviral proliferation even in the presence of CUG2 but inhibition of ERK, JNK and Src kinase does not, indicating that activation of p38 MAPK and Ras has critical roles in reoviral replication in CUG2-expressing tumor cells. Accordingly, we propose that reovirus can be useful in the treatment of transformed cells expressing CUG2, which is commonly detected in various tumor tissues.

Inhibition of GSK-3beta enhances reovirus-induced apoptosis in colon cancer cells

Reovirus functions as an oncolytic agent for many types of cancer including colon cancer. Although most studies have emphasized the role of activated Ras signaling in enhancing reoviral oncolysis in susceptible cells, we note that many colon cancers also display elevated beta-catenin. Thus, it is possible that enhanced beta-catenin may augment reoviral susceptibility in colon cancer cells. To explore this hypothesis, HEK293 cells were treated with the glycogen synthase kinase (GSK)-3beta inhibitor LiCl, thereby inducing beta-catenin, followed by reoviral infection. Co-administration with LiCl indeed enhanced cell death compared to reovirus infection alone, but this was not associated with elevated reoviral replication. Similarly, HEK293 cells expressing the Frizzled-1 receptor in Wnt3a-conditioned medium also showed reovirus replication equivalent to that in cells in control medium, further suggesting that up-regulation of beta-catenin does not enhance the replication of reovirus. Instead, we observed that inhibition of GSK-3beta with LiCl decreased reovirus-induced NF-kappaB activation, leading to accelerated apoptosis via caspase 8 activation. We further found that colon cancer HCT116 cells were sensitized to apoptosis by co-treatment with reovirus and a GSK-3beta inhibitor, AR-A014418. Finally, we identified that inhibition of NF-kappaB sensitized apoptosis of HEK293 or HCT 116 cells during reovirus infection. Taken together, we propose that inhibition of GSK-3beta sensitizes reovirus-induced apoptosis of colon cancer cells by down-regulation of NF-kappaB activity, offering a potentially improved therapeutic strategy for the treatment of colon cancer.

PAUF functions in the metastasis of human pancreatic cancer cells and upregulates CXCR4 expression

Pancreatic cancer is characterized by early metastatic spread, but the process of tumor cell dissemination is largely unknown. In this study we show that the soluble protein pancreatic adenocarcinoma upregulated factor (PAUF) has an important role in the metastasis and progression of the disease. Variations in the level of PAUF, either by overexpression or knockdown, resulted in altered migration, invasion and proliferation capacity of pancreatic cancer cells. Moreover, depletion of PAUF in metastatic cells dramatically abrogated the spread of the cells to distant organs in an orthotopic xenograft mouse model. PAUF elicited the activation of the extracellular signal-regulated kinase (ERK), c-Jun N-terminal kinase (JNK) and AKT intracellular signaling cascades and consequently their downstream transcription factors in an autocrine manner. Genome-wide expression analysis revealed that C-X-C chemokine receptor type 4 (CXCR4) expression was induced by PAUF overexpression but was repressed by PAUF knockdown. The PAUF-mediated increase in cancer cell motility was attenuated by the CXCR4 inhibitor, AMD3100, or by anti-CXCR4 antibody. Furthermore, immunohistochemical analysis of pancreatic tumor tissues clearly showed a significant positive correlation between PAUF and CXCR4 expression. Collectively, these findings indicate that PAUF enhances the metastatic potential of pancreatic cancer cells, at least in part, by upregulating CXCR4 expression.

Identification of novel reference genes using multiplatform expression data and their validation for quantitative gene expression analysis

Normalization of mRNA levels using endogenous reference genes (ERGs) is critical for an accurate comparison of gene expression between different samples. Despite the popularity of traditional ERGs (tERGs) such as GAPDH and ACTB, their expression variability in different tissues or disease status has been reported. Here, we first selected candidate housekeeping genes (HKGs) using human gene expression data from different platforms including EST, SAGE, and microarray, and 13 novel ERGs (nERGs) (ARL8B, CTBP1, CUL1, DIMT1L, FBXW2, GPBP1, LUC7L2, OAZ1, PAPOLA, SPG21, TRIM27, UBQLN1, ZNF207) were further identified from these HKGs. The mean coefficient variation (CV) values of nERGs were significantly lower than those of tERGs and the expression level of most nERGs was relatively lower than high expressing tERGs in all dataset. The higher expression stability and lower expression levels of most nERGs were validated in 108 human samples including formalin-fixed paraffin-embedded (FFPE) tissues, frozen tissues and cell lines, through quantitative real-time RT-PCR (qRT-PCR). Furthermore, the optimal number of nERGs required for accurate normalization was as few as two, while four genes were required when using tERGs in FFPE tissues. Most nERGs identified in this study should be better reference genes than tERGs, based on their higher expression stability and fewer numbers needed for normalization when multiple ERGs are required.